The present invention relates to the field of machine tools, and more particularly to machine tools in which one or more machining heads operate horizontally, pressing axially on a workpiece to be machined by chip removal.
Because of the speed of operation of the modern machining heads used at present, and the speed of the movements imparted to them when they approach the workpiece, the said machining heads are subjected to considerable axial stresses, caused both by inertial phenomena and by forces which they exchange with the workpiece.
Consequently, the aforesaid machining heads tend to vibrate axially during operation, so that the position of the tool relative to the workpiece is modified from one instant to the next, according to the extent of the said axial stresses. This naturally gives rise to machining inaccuracies which are usually unacceptable.
These problems are aggravated by the fact that, in machines of the type described above, the machining heads are mounted horizontally on a vertical bed, fixed to supporting structures, which, as a result of the said stresses, is bent elastically, thus modifying the amplitude of the vibrations of a machining head in proportion to the square of the vertical distance between the machining head and the point at which the bed is fixed to the supporting structure.
There are two main types of arrangement used at the present time to compensate for the problems described above, or at least to limit their effects; the first of these arrangements consists in significantly increasing the mass of the bed and its characteristics of elastic yielding to bending, and the second consists in moderating both the operating speed and the speed of movement of the machining heads.
Clearly, both of these arrangements cause other problems, such as a considerable weight and cost, and a decrease in the output rate of the machine tool.